Previous studies have demonstrated that pleasant touch activates reward-related cortical regions including the anterior prefrontal cortex (APFC) in adults, but the developmental change is still unknown in infancy. The present study used near infrared spectroscopy (NIRS) to investigate activation of the APFC by gentle touching of the hand of infants 2-16 months after birth, who were classified into three groups (3, 6 and 10 months old). Results showed that 10-month-olds, but not 3- and 6-month-olds, showed bilateral activation of the APFC by gentle touching of the palm with a sensuous velvet fabric compared to touch with rounded wood. The present finding suggests that developmental changes in the tactile affective system are associated with the activation of the APFC and that the critical point is between 6 and 10 months after birth.
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